1. Field of the Disclosure
The present disclosure relates to an improved antistatic system and a process for making the antistatic system and use of the antistatic system in thermoplastic polymer compositions to impart antistatic properties to the resultant plastic parts.
2. Description of the Related Art
High molecular weight polymers, for example, hydrocarbon polymers and polyamides, are melt extruded into shaped structures such as tubing, pipe, wire coating or film by well-known procedures wherein a rotating screw pushes a viscous polymer melt through an extruder barrel into a die in which the polymer is shaped to the desired form, and is then subsequently cooled and solidified into a product, that is, the extrudate, having the general shape of the die. In film blowing processes, as an extruded plastic tube emerges from the die, the tube is continuously inflated by air, cooled, collapsed by rolls and wound up on subsequent rolls.
Inorganic pigments may also be added to the thermoplastic polymer. In particular, titanium dioxide pigments are added to thermoplastic polymers for imparting whiteness and/or opacity to the finished article. To deliver other properties to the molded part or film, additional additives are incorporated into the processing step. What is needed is a titanium dioxide that has multiple properties associated with it.
One of these properties is charge dissipation known as antistatic. Additive treatment with an anti-electrostatic (“antistatic”) agent can reduce the surface resistance and dust-attracting tendency of plastics. In order to get this property in light reflective or colored films, that is; those that are not black, a separate additive known as an antistatic agent may be added to the polymer composition during processing. This process adds additional cost and complexity to the process. What is needed is a non black pigment which imparts color and opacity along with charge dissipation properties.
Commercially available additives for antistatic treatment of plastics are, for example, alkyl-sulfonates, ethoxylated alkylamines, quaternary ammonium, and phosphonium salts and fatty acid esters. Specific polyalkylane ethers/polyalkylene glycols have also been described for antistatic treatment of plastics. Other examples of antistatic additives that have been described are ethoxylated long-chain aliphatic amines, long chain aliphatic amines, and amides, and phosphate esters.
Certain polysiloxanes have been known as “superwetters” for use in agricultural sprays, such as herbicides, fungicides or insecticides, for facilitating wet-out of the spray onto the plant or plant leaves to enhance application of the agricultural spray to the plant or plant leaf. Use of such polysiloxanes to improve the performance of antistatic agents in plastics is not known.
U.S. Pat. No. 6,497,933 discloses antistatic coatings containing an organic cationic polymeric electrolyte, a binder, and Silwet L-77 sold by Osi Specialties of Danbury, Conn. as a surfactant. The '933 patent describes applying the antistatic coating to a film surface. Nothing in the '933 patent teaches or suggests that Silwet 77 has antistatic properties or mixing Silwet 77 into a thermoplastic polymer melt would synergistically improve the performance of a migratory antistatic agent.
U.S. Pat. No. 5,401,871 discloses organopolysiloxane polyethers said to have increased resistance to hydrolysis. The '871 patent does not teach or suggest synergistic behavior of the organopolysiloxane polyethers with antistatic agents.